The Anglo-Dutch oil giant confirmed on Wednesday that its offices had been “visited” by anti-fraud investigators in February.

A spokesman for Shell said: “The visit was related to OPL 245, an offshore block in Nigeria that was the subject of a series of long-standing disputes with the federal government of Nigeria. Shell is cooperating with the authorities and is looking into the allegations, which it takes seriously.”

The Italian newspaper Corriere della Sera reported that the Dutch Financial Intelligence and Investigation Service (FIOD) and the Dutch public prosecutor had raided the multinational’s office in the Hague.

The oil block is estimated to contain up to 9bn barrels of crude, and has been at the centre of a series of disputes since 1998.

Dan Etete, who was oil minister in Nigeria under the military dictator general Sani Abacha, awarded the oil block to a company called Malabu oil.

The field was subsequently sold in 2011 to Eni and Shell. Shell and Eni paid the Nigerian government, but $1.09bn was subsequently sent to Malabu.

Shell and Eni both insist that they did not know this would happen.

The probe into Eni was triggered after an intermediary in the deal, Emeka Obi, sued Malabu in Britain’s high court.

In response to the news that it is being drawn into the investigation a spokesman said: “Shell attaches the greatest importance to business integrity.

“It’s one of our core values and is a central tenet of the principles that govern the way we do business. All employees are expected to uphold these principles and failure to do so will result in consequences up to and including dismissal.”